The present invention relates to a modified xe2x8ax96-Al2O3-supported nickel reforming catalyst and its use for producing synthesis gas from natural gas. More particularly, the present invention is to provide a nickel reforming catalyst expressed by the following formula 1, having improved coke resistance, high-temperature catalysis stability and catalytic activity, which is prepared by coating nickel or mixture of nickel and cocatalyst (M1-M2-Ni) on a xe2x8ax96-Al2O3 support modified with metal (M3-M4-ZrO2/xe2x8ax96-Al2O3), and its use for producing synthesis gas from natural gas through steam reforming, oxygen reforming or steam-oxygen reforming,
M1-M2-Ni/M3-M4-ZrO2/xe2x8ax96-Al2O3xe2x80x83xe2x80x83(1) 
wherein M1 is an alkali metal; each of M2 and M3 is an alkaline earth metal; and M4 is a IIIB element or a lanthanide.
Steam reforming, which produces a mixture (synthesis gas) of hydrogen and carbon monoxide from methane (natural gas), has become an important and fundamental chemical industrial process from long time ago. Synthesis gas produced by steam reforming of methane is widely used for producing methanol, hydrogen, ammonia, etc. Recently, it has been used for producing liquid fuel or oxygen-including compounds.
The biggest problem in the steam reforming is deactivation of reforming catalyst due to deposition of carbon. The carbon deposition can be calculated thermodynamically from molar ratios of hydrogen to carbon and oxygen to carbon in the product. Therefore, in steam reforming of methane, excess amount of steam is required to increase molar ratios of hydrogen to carbon and oxygen to carbon, in order to prevent deactivation of reforming catalyst. This promotes an aqueous gasification enough to obtain a synthesis gas with molar ratio of hydrogen to carbon monoxide larger than 3:1. Therefore, this process may be suitable for producing ammonia or high-concentration hydrogen. The current industrial steam reforming process of methane is being carried out under the condition of 730-860xc2x0 C. of a temperature, 20-40 atm of a pressure and 1:4-6 of methane-to-steam molar ratio.
And, for the industrial catalyst for the steam reforming, nickel catalyst is used dominantly. A superior industrial reforming catalyst should have coke resistance and thermal and mechanical stability. For this purpose, selection of suitable support such as xcex1-alumina is very important.
The inventors suggested reforming, reactions using modified zirconia-supported nickel catalyst. [Korea Patent Application No. 99-50013; Korea Patent Application No. 2000-0054443; and Korea Patent Application No. 2000-0057688]. Korea Patent Application No. 99-50013 discloses a modified zirconia-supported nickel catalyst and carbon dioxide reforming using it. Korea Patent Application No. 2000-0054443 discloses a cerium-modified zirconia-supported nickel catalyst and steam reforming using it. Further, Korea Patent Application No. 2000-0057688 discloses a modified zirconia-supported nickel catalyst and steam-oxygen reforming using it. The modified zirconia-supported nickel catalyst showed better activity and stability than those of conventional reforming catalysts when used in carbon dioxide reforming, steam reforming, and steam-oxygen reforming even under severe condition (high space velocity and low steam-to-methane ratio) and at high temperature. Despite of good activity and stability, zirconia is not suitable to be used in reforming catalyst, because it is more expensive than alumina. Accordingly, it is required to use the more cost-effective xe2x8ax96-Al2O3 support and modify it with zirconia. Then, if it is coated with nickel catalyst, an inexpensive catalyst with good activity and stability can be obtained.
Inventors have developed a nickel reforming catalyst by coating xe2x8ax96-Al2O3 base support with zirconia modified with alkaline earth metal (M3) and IIIB element or lanthanide metal (M4), and coating nickel and alkali metal (M1) or alkaline earth metal (M2) cocatalyst. When this reforming, catalyst was used in various reforming reactions of natural gas, i.e., steam reforming, oxygen reforming or steam-oxygen reforming, it has showed equal or superior activity and stability compared with the modified zirconia-supported nickel catalyst we had suggested in Korea Patent Application No. 99-50013.
Accordingly, an object of the present invention is to provide a nickel reforming catalyst using xe2x8ax96-Al2O3 as base support, and its use for producing synthesis gas through reforming reaction.